How Estrous Cycle Hormones Reach the Brain

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How internal states like hunger and hormones shape instinctive behaviors, particularly parental care

Episode Summary: Dr. Johannes Kohl explains instinctive behaviors in mammals, emphasizing how states like hunger and hormonal cycles modulate actions such as parental care; they discuss hypothalamic circuits, hormone integration, and pregnancy-induced brain changes, highlighting the balance between motivations like feeding and nurturing offspring.

About the guest: Jonny Kohl, PhD heads the State-Dependent Neural Processing Lab at the Francis Crick Institute in London.

Discussion Points:

• Instinctive behaviors: Pre-wired actions like escaping predators or parental care enable survival without learning, yet remain modifiable by experience and internal states.
• Internal states: Defined as slowly changing conditions (minutes to weeks) like hunger or hormonal fluctuations that influence brain processing & behavior prioritization.
• Hunger regulation: Hypothalamic AGRP neurons detect caloric deficits, creating motivational discomfort relieved by food anticipation, operating on multiple timescales via neurotransmitters & peptides.
• Parental care: Virgin mice show variable pup-directed behaviors; hunger increases aggression, modulated by estrous cycle hormone ratios (estradiol/progesterone).
• Hormone-brain interactions: Steroid hormones like estradiol and progesterone diffuse into the brain, altering gene expression, neuronal excitability, and circuit plasticity over short and long timescales.
• Pregnancy adaptations: Late pregnancy rewires MPOA circuits via surging hormones, preparing robust maternal behavior before birth (anticipatory brain plasticity).

Practical Takeaways:

• Recognize hunger’s impact: Mild food deprivation can heighten irritability or aggression, which can affect social interactions.
• Consider hormonal influences: Cyclical hormone changes affect mood and motivation; tracking cycles may help predict and manage behavioral shifts.
• Prioritize self-care in parenting: Sleep and nutrition deficits mimic hunger states, potentially reducing patience; ensure rest and meals to support nurturing behaviors.
• Question chronic hormone use: Long-term interventions like birth control or testosterone can alter brain function; weigh benefits against potential side effects.

*Not medical adv

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